JP4487440B2 - Failure diagnosis device for evaporative fuel treatment equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for diagnosing a failure of a fuel vapor processing apparatus for preventing vaporized fuel generated in a fuel tank from being released into the atmosphere.
[0002]
[Prior art]
Japanese Patent Application Laid-Open No. 2000-282972 discloses a first failure diagnosis means (mode C) for diagnosing a large leak failure of about 0.5 inches in diameter in a predetermined region using engine speed and engine load as parameters, and a throttle in the predetermined region. A failure diagnosis device for an evaporated fuel processing device having second failure diagnosis means (mode B) for diagnosing a small leak failure of about 0.02 inches in diameter on the condition that the change in opening is small is disclosed.
[0003]
[Problems to be solved by the invention]
In the conventional failure diagnosis device, a large leak failure is detected by a negative pressure introduction failure. Specifically, if the tank internal pressure does not become lower than a predetermined value within a predetermined time in a negative pressure introduction state, a negative pressure introduction failure is detected. That is, it is determined as a large leak failure. When such a determination method is adopted, a predetermined region where a large leakage failure diagnosis is executed is inevitably determined because an intake negative pressure that can achieve a predetermined pressure reduction state within a predetermined time in a normal state is necessary. Therefore, it becomes an engine operation region in which a certain amount of intake negative pressure is obtained. Unlike the above-mentioned large leak failures, small leak failures have a method of performing failure diagnosis by detecting the degree of pressure increase in a sealed state after reducing to a predetermined negative pressure. Is in the same predetermined area as the large leakage failure with respect to engine speed and engine load.
[0004]
Small leak failures are diagnosed based on the degree of pressure increase after decompression, so it is not always necessary to make the intake negative pressure sufficient to achieve a prescribed decompression state within a prescribed time. Even if time is required, diagnosis can be made if a predetermined reduced pressure state can be achieved. However, the conventional one simply makes the diagnosis area of a small leak failure the same as the diagnosis area of a large leak failure without considering such points at all, so that the diagnosis area of a small leak failure is unnecessarily narrow. As a result, there is a problem that the opportunity for failure diagnosis is reduced.
[0005]
Further, the conventional one sets another diagnostic means (mode A) for diagnosing a small leak failure during idling when the engine speed is higher than a predetermined engine speed and during air-fuel ratio footback control. However, there is a problem of increasing the complexity of the control logic and the like, and it is not possible to increase the diagnosis opportunities efficiently.
SUMMARY OF THE INVENTION An object of the present invention is to provide a failure diagnosis device for an evaporative fuel processing apparatus that improves failure diagnosis performance by increasing failure diagnosis opportunities without problems.
[0006]
[Means for Solving the Problems]
In the failure diagnosis apparatus for the evaporated fuel processing apparatus according to the present invention, the evaporated fuel purge path connecting the fuel tank and the engine intake passage is blocked from the atmosphere and the engine intake negative pressure is introduced in the fuel tank. A first failure diagnosis means for monitoring a pressure decrease degree and diagnosing a failure corresponding to a large hole; and monitoring a pressure increase degree in a sealed state where the pressure inside the fuel tank is reduced to a predetermined negative pressure and then shut off from the atmosphere. Second failure diagnosis means for performing failure diagnosis corresponding to the small holes, the operation area of the second failure diagnosis means substantially including the operation area of the first failure diagnosis means, and the operation area of the first failure diagnosis means It is set to expand to a lower intake negative pressure side.
[0007]
According to the present invention, the first failure diagnosing means for diagnosing the failure corresponding to the large hole is in a state where the purge path of the evaporated fuel connecting the fuel tank and the engine intake passage is shut off from the atmosphere and the engine intake negative pressure is introduced. This is a method for detecting the negative pressure introduction failure by monitoring the pressure decrease degree in the fuel tank, so that the operating region is naturally determined by the balance with the engine intake negative pressure. The second failure diagnosis means for performing the failure diagnosis corresponding to the small hole is a method of detecting the pressure increase degree in a sealed state where the pressure inside the fuel tank is reduced to a predetermined negative pressure and then shut off from the atmosphere. Even if the pressure decrease degree is small, it can be diagnosed if the pressure can be reduced to a predetermined negative pressure. Therefore, in the present application in which the operation region of the second failure diagnosis unit is substantially set to the lower intake negative pressure side than the operation region of the first failure diagnosis unit, substantially including the operation region of the first failure diagnosis unit, Thus, the failure diagnosis opportunities by the second failure diagnosis means can be increased without problems.
[0008]
As a preferred embodiment, the operating area of the first and second failure diagnosis means is determined by setting the engine speed and the engine load as parameters, respectively, and the operation area of the second failure diagnosis means is lower than the operation area of the first failure diagnosis means. By setting so as to include the side and / or the low rotational speed side, it is possible to easily set the optimum operation region for each of the first and second failure diagnosis means.
Further, if the operation area of the second failure diagnosis means is set so as to completely include the operation area of the first failure detection means, only the failure diagnosis corresponding to the large hole will not be executed. The reliability of failure diagnosis can be ensured without being judged as normal under the situation where it occurs.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the evaporative purge system that is an evaporative fuel processing apparatus according to the present embodiment releases vaporized fuel (vapor) generated in a fuel tank 1 installed in a vehicle such as an automobile into the atmosphere. It is for preventing. In this system, the vaporized fuel from the fuel tank 1 is introduced into the canister 3 connected to the vapor passage 2 through the vapor passage 2, and the vaporized fuel adsorbed in the canister 3 is passed through the purge passage 4 under predetermined conditions. It is configured to discharge (purge) into the intake passage 6 of the internal combustion engine 5.
[0010]
The purge passage 4 is provided with a purge solenoid valve 7 as an opening / closing means for opening and closing the passage. The canister 3 is provided with a vent solenoid valve 8 that opens and closes the air introduction part 12. The purge solenoid valve 7 and the vent solenoid valve 8 are used for failure diagnosis. The purge solenoid valve 7 and the vent solenoid valve 8 are connected to an engine control unit (hereinafter referred to as “ECU”) 11 as control means, and are controlled to be opened and closed based on a control signal from the ECU 11. ing.
[0011]
As shown in FIGS. 6 and 7, the purge solenoid valve 7 is opened when the purge solenoid valve 7 is turned on to open the purge passage 4, and when it is turned off, the purge solenoid valve 7 is closed and closes the purge passage 4. The vent solenoid valve 8 opens the atmosphere introduction part 12 when turned off, and closes the atmosphere introduction part 12 when turned on. In this evaporation purge system, the purge solenoid valve 7 is normally turned on and the vent solenoid valve 8 is turned off. When a determination condition for determining a failure is established, when the purge solenoid valve 7 is turned off and the purge passage 4 is closed, and the vent solenoid valve 8 is turned on and the atmosphere introduction part 12 is closed, the inside of the fuel tank 1 is large. Increase the pressure to about atmospheric pressure. When the purge solenoid valve 7 is turned on in this state and the purge passage 4 is opened, the fuel tank 1 and the intake passage 6 communicate with each other via the vapor passage 2 and the purge passage 4, and the negative pressure in the intake passage 6 causes the negative pressure action. The tank internal pressure is reduced.
[0012]
A fuel level sensor 9 as fuel remaining amount detecting means is attached to the fuel tank 1 so that the fuel remaining amount in the tank can be detected. The fuel tank 1 is provided with a pressure sensor 10 serving as a pressure detecting means as a situation detecting means so that the pressure in the tank can be detected. The detection information from the fuel level sensor 9 and the pressure sensor 10 is sent to the ECU 11. A detachable filler cap 16 is attached to the fuel filler port 17 of the fuel tank 1. The filler cap 16 is configured so that when the fuel cap 17 is normally attached to the fuel filler port 17, the fuel filler port 17 is hermetically sealed so that the atmosphere is not introduced into the fuel tank 1 from the fuel filler port 17.
[0013]
The evaporation purge system configured as described above includes a failure diagnosis device that detects a leakage failure of the evaporation purge system in order to prevent the vaporized fuel from being released into the atmosphere due to the failure of the evaporation purge system. This failure diagnosis device controls the purge solenoid valve 7 and the vent solenoid valve 8 to monitor the pressure drop degree (ΔPD) and the pressure rise degree (ΔP) in the fuel tank 1 to make a failure determination. is there.
[0014]
The failure diagnosis device controls the purge solenoid valve 7 and the vent solenoid valve 8 to monitor the pressure reduction degree ΔPD in the fuel tank 1 in a state where the purge path 4 is shut off from the atmosphere and the engine intake negative pressure is introduced. The first failure diagnosis means 13 for performing failure diagnosis corresponding to a large hole and the purge solenoid valve 7 and the vent solenoid valve 8 are controlled to reduce the pressure in the fuel tank 1 to a predetermined negative pressure and then shut off from the atmosphere. A second failure diagnosis means 14 for monitoring the pressure rise degree ΔP in the state and performing a failure diagnosis corresponding to the small hole, and a selection means 15 for selecting the first failure diagnosis means 13 or the second failure diagnosis actual means. Yes. In the present embodiment, the ECU 11 includes the first failure diagnosis unit 13, the second failure diagnosis unit 14, and the selection unit 15.
[0015]
FIG. 2 is a diagram illustrating an operation region A in which the first failure diagnosis unit 13 operates and an operation region B in which the second failure diagnosis unit 14 operates. In the figure, the vertical axis represents the load Ev of the engine and the horizontal axis represents the engine speed Ne. In this embodiment, the operation region B substantially includes the operation region A, and is set to be enlarged toward the low intake negative pressure side from the operation region A. In other words, the operating regions A and B each define the engine speed Ne and the load Ev as parameters. The operating region B includes a lower load side and / or a lower engine speed side than the operating region A, and the operating region B operates. The area A is set to be completely included.
[0016]
In this embodiment, the failure diagnosis corresponding to small holes is for diagnosing the presence or absence of leakage from a hole of about 1.0 mm, and the failure diagnosis corresponding to large holes is from a hole larger than 1.0 mm. It diagnoses a state in which the leak or filler cap 16 is not tightened. In a memory (not shown) of the ECU 11, a leak determination value M used by the first failure diagnosis unit 13 and a leak determination value L used by the second failure diagnosis unit 14 are stored in advance.
[0017]
Next, the operation of the first failure diagnosis means 13, the second failure diagnosis means 14, and the selection means 15 will be described based on the flowcharts shown in FIGS.
In FIG. 3, in step R1, the engine speed Ne and the load Ev are read from detection means such as a rotation sensor and a throttle opening sensor (not shown), and each operation such as water temperature, intake air temperature, air-fuel ratio learning value, remaining fuel amount, etc. The state is read, and in step R2, it is determined whether the operating state excluding the engine speed Ne and the engine load Ev satisfies a predetermined condition for executing the first failure diagnosis. If the condition is satisfied, it is determined in step R3 whether or not the engine is in the operation region A using FIG. 2 from the engine speed Ne and the engine load Ev. If it is the operation region A, the process proceeds to step R4, the first failure diagnosis means 13 is selected, and the first failure diagnosis means described later is executed.
[0018]
After the execution of the first failure diagnosis at step R4 is completed, or when the execution condition is not satisfied at step R2, or when it is not the A region at step R3, the process proceeds to step R5. In this step, it is determined whether or not the operating state excluding the engine speed Ne and the engine load Ev satisfies a predetermined condition for executing the second failure diagnosis. If the condition is satisfied, it is determined in step R6 from the engine speed Ne and the engine load Ev whether or not it is the operation region B using FIG. If it is the operation region B, the process proceeds to step R7, the second failure diagnosis means 14 is selected, and the second failure diagnosis means described later is executed. Note that after the execution of the second failure diagnosis at step R7 is completed, or when the execution condition is not satisfied at step R5, or when it is not the B region at step R6, the process ends.
[0019]
FIG. 4 shows the details of the processing by the second failure diagnosis means 14 performed in step R7 in FIG. In the second failure diagnosis means 14, the purge solenoid valve 7 is turned on in step S1 to reduce the tank internal pressure to the predetermined negative pressure P2 shown in FIG. Proceed to In step S2, the amount of increase in the internal pressure of the fuel tank 1 is measured (see FIG. 6), and in step S3, the pressure increase degree ΔP (the amount of increase in pressure from the predetermined negative pressure P2) is calculated from the measurement result. In step S4, the pressure increase degree ΔP and the leak judgment value L are compared. If the pressure rise degree ΔP does not exceed the leak judgment value L, it is determined that there is no leak in the evaporation purge system, and the belt solenoid The valve 8 is turned off to end the second failure diagnosis.
[0020]
If the degree of pressure increase ΔP exceeds the leak judgment value L in step S4, it is assumed that there is a possibility that the fuel system has a leak (leakage). In step S5, a state with a leak is counted, and the number of counts is previously stored in the memory of the ECU 11 in step S6. It is determined whether or not the predetermined number of times stored in the memory is reached. If the predetermined number of times has not been reached, the steps from step S1 to step S6 are repeated to increase the reliability, and the number of counts at which the pressure increase degree ΔP exceeds the leak determination value L is a predetermined number of times, for example, two times. If it exceeds, the process proceeds to step S7 because there is a leak, a warning lamp (not shown) is turned on to warn of a failure, and the belt solenoid valve 8 is turned off to complete the second failure diagnosis.
[0021]
FIG. 5 shows the details of the processing by the first failure diagnosis means 13 performed in step R4 in FIG. In the first failure diagnosis, the purge solenoid valve 7 is controlled to be turned on in step T1, and the process proceeds to step T2. In step T2, the amount of decrease in the fuel tank internal pressure is measured for a predetermined time. In step T3, a pressure drop degree ΔPD is calculated from the measurement result. Here, the pressure drop degree ΔPD of the tank internal pressure that has fallen within a predetermined time after the purge solenoid valve 7 is turned on is calculated. In step T4, the pressure drop degree ΔPD is compared with the leak determination value M.
[0022]
As indicated by a broken line in FIG. 7, the tank pressure P3 at the time when the measurement time has elapsed is higher than a predetermined negative pressure P1 (corresponding to ΔPD = M), and the pressure drop degree ΔPD is the reference pressure drop degree as the leak judgment value M. If not, the process proceeds to step T5 assuming that the evaporation purge system has a large hole. In step T5, a warning lamp (not shown) is lit to warn of a failure, the process proceeds to step T6, the belt solenoid valve 8 is turned off, and the first failure diagnosis is finished. When the pressure drop degree ΔPD exceeds the leak determination value M in step T4, it is assumed that there is no large hole, and the processing after step R5 in FIG. 3 is subsequently performed to perform the second failure diagnosis corresponding to the small hole. .
[0023]
In this way, when performing the failure diagnosis, the operation region B of the second failure diagnosis unit 14 substantially includes the operation region A of the first failure diagnosis unit 13 and is lower than the operation region of the first failure diagnosis unit. By setting the expansion to the negative pressure side, it is possible to increase the failure diagnosis opportunities by the second failure diagnosis unit 14 without any failure by effectively utilizing the difference in characteristics between the two failure diagnosis units, and to improve the failure diagnosis performance. .
[0024]
In the second failure diagnosing means 14 for performing the small hole diagnosis, the pressure rise degree ΔP in the fuel tank 1 is detected and diagnosed a plurality of times in consideration of electric noise, accuracy error, etc., so that the diagnosis accuracy is improved. Can do.
Further, since the operation region B includes a lower load side and / or a lower rotation speed side than the operation region A, the optimal operation region for each of the first and second failure diagnosis means 13 and 14 can be easily set. Further, since the operation region B completely includes the operation region A, only failure diagnosis corresponding to the large hole is not performed, so that the normal determination is made under a situation where leakage due to the small hole occurs. Therefore, reliability of failure diagnosis can be ensured.
[0025]
【The invention's effect】
According to the present invention, the first failure diagnosing means for diagnosing a failure corresponding to a large hole is a method of detecting a negative pressure introduction failure, so that the operating region is naturally determined by the balance with the engine intake negative pressure. The second failure diagnosing means for performing the corresponding failure diagnosis can be diagnosed if the pressure can be reduced to a predetermined negative pressure even if the degree of pressure decrease at the time of introducing the negative pressure is small. By effectively setting the lower intake negative pressure side than the operating region of the first failure diagnostic means, substantially including the operating region of the diagnostic means, the difference between the characteristics of both failure diagnostic means can be effectively utilized by the second failure diagnostic means. Failure diagnosis opportunities can be increased without problems, and failure diagnosis performance can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an evaporated fuel processing device and a failure diagnosis device according to an embodiment of the present invention.
FIG. 2 is a diagram showing operating areas of first and second failure diagnosis means, respectively.
FIG. 3 is a flowchart for selecting first or second failure diagnosis means;
FIG. 4 is a flowchart showing one form of second failure diagnosis.
FIG. 5 is a flowchart showing one form of first failure diagnosis.
FIG. 6 is a time chart for explaining a second failure diagnosis.
FIG. 7 is a time chart for explaining the first failure diagnosis.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fuel tank 4 Purge path | route 6 Engine intake passage 14 1st failure diagnostic means 15 2nd failure diagnostic means A Operation area B of 1st failure diagnosis means Operation area ΔP of 2nd failure diagnosis means ΔPD Pressure increase degree ΔPD Pressure decrease degree

Claims (1)

Diagnose faults in response to large holes by monitoring the pressure decrease in the fuel tank with the engine intake negative pressure introduced while the purge path of the evaporated fuel connecting the fuel tank and the engine intake passage is shut off from the atmosphere. First failure diagnosis means to perform;
A second failure diagnosing means for diagnosing a failure corresponding to a small hole by monitoring the degree of pressure increase in a sealed state that is shut off from the atmosphere after the inside of the fuel tank is depressurized to a predetermined negative pressure,
The operating region of the second failure diagnosis means substantially includes the operation region of the first failure diagnosis means, and is set to be expanded to the low intake negative pressure side from the operation region of the first failure diagnosis means. Device fault diagnosis device.

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